The triquetra has been found on runestones in Northern Europe and on early Germanic coins. It presumably had pagan religious meaning and it bears a resemblance to the Valknut, a symbol associated with Odin.
G Scale Trains are usually referred to as Garden Trains since they are the largest of the model trains and are used outdoors as well as indoors.
Here is a simple page designed to allow you to Identify the type of train you have by the type of track it uses. I buy all scales of trains. Z Scale - Extremely small Trains, they make several Briefcase type trains. Primarily Made by Marklin and called Mini Club.